The major objective is to identify etiologic agents in systemic lupus erythematosus (SLE), and rheumatoid arthritis (RA), by methods based on nucleic acid hybridization and related techniques. DNA or RNA from tissue or blood specimens from patients with these disorders will be examined in this way. Similarly, recent techniques developed for examining the role of C-type agent in other disorders will be applied to the examination of this material. Secondary goals relate to investigating more proximate pathogenetic mechanisms in these diseases, using similar techniques, as well as to using any information so-derived for immediate clinical application where possible. In this regard studies will be continued into the use of synthetic nDNA antigens for examining anti-DNA antibodies more extensively as well as to further explore the clinical and pathological significance of circulating DNA.